General Mills hit a snag when it wanted to give Lucky Charms a healthier makeover. The breakfast cereal powerhouse tried for two long years, but couldn't figure out how to manufacture the "magically delicious" cereal without artificial colors and flavors.

Maintaining the vibrancy of the colors in Lucky Charms' little marshmallows while not profoundly altering their flavor has stumped food scientists.

General Mills had six to seven people working full time on the project for two years, but they couldn't crack the code to make the colorful chewy marshmallows "all natural." So efforts have stalled.

Each marshmallow "brings a different challenge to the table for us," Kate Gallagher, a cereal recipe developer at General Mills, told Quartz.

The effort was part of a companywide push to phase out artificial colors and flavors.

"People eat with their eyes," said Jim Murphy, a General Mills division president, in a YouTube video when the effort launched in 2015. "And so food has to look appealing, and bright colors give it an appealing look. People don't want (artificial) colors with numbers in their food anymore."

With cereal sales on the decline in recent years, General Mills had pinned some hopes on attracting more sales by putting a health-conscious spin on its traditional breakfast brands.

For now, Lucky Charms can claim to be on top of one trend: It's gluten-free, except for the chocolate version. And in the spirit of embracing what it can't change, Lucky Charms' latest promotion offers 10,000 winners a box full of only the little artificially flavored marshmallows.